1. Field of the Invention
The present invention relates to a pulse tube refrigerator adapted to generate the cold at an endothermic portion by connecting a cold accumulator and a pulse tube to each other so as to supply and discharge gas to and from a compressor, and more specifically to a double inlet pulse tube refrigerator adapted to switch gas supply from a compressor to a high-temperature side of a pulse tube.
2. Description of Prior Art
Conventionally, as a pulse tube refrigerator which is capable of obtaining a lower attainable temperature there has been proposed a double inlet pulse tube refrigerator illustrated in FIG. 3 (described in the scientific essay "CRYOGENICS" September 1990). In this double inlet pulse tube refrigerator, a low-temperature end (5) of a pulse tube (50) is communicated with a low temperature end (53) of a cold accumulator (52) through an endothermic connection pipe (54) serving as a cold head so that gas to be supplied from a compressor (55) to a high-temperature end (57) of the cold accumulator (52) through a refrigerant gas passage (56) can be introduced from the low-temperature end (51) of the pulse tube (50) to a high-temperature end (58) thereof through the cold accumulator (52) and the endothermic connection pipe (54), a phase shifter comprising a needle valve (59) and a a buffer tank (60) is arranged in the high-temperature end (58), a branch gas passage (61) branched off from the refrigerant gas passage (56) is connected to a passage portion between the high-temperature end of the pulse tube (50) and the buffer tank (60), a needle valve (62) is arranged in the branch gas passage (61), and water coolers (63) (64) are disposed at the high-temperature ends of the cold accumulator (52) and the pulse tube (50) so as to apply a water cooling to the high-temperature end portions of the cold accumulator (52) and the pulse tube (50).
In this double inlet pulse tube refrigerator, since the high-temperature end portions of the cold accumulator (52) and the pulse tube (50) are adapted to be water-cooled, water coolers (63) (64) are directly connected to the refrigerator, which causes a problem that the refrigerator becomes large in size. Further, since the needle valve (59) is arranged between the pulse tube (50) and the buffer tank (60) as well as the needle valve (62) is arranged in the branch gas passage (61) connecting the refrigerant gas passage (56) to the passage portion between the high-temperature end portion of the pulse tube (50) and the buffer tank (60), there is a problem that the gas flow is disturbed by these needle valves (59) (62) to generate swirls. Additionally, in this double inlet pulse tube refrigerator, since the compressor section of the reciprocating type is rigidly connected to the cold generating section, there is also such a problem that vibrations of the compressor is transmitted to the cold generating section so that this refrigerator can't be used for cooling machinery and parts which hate vibrations.
Thereupon, the applicant of the present invention has proposed such a double inlet pulse tube refrigerator (disclosed in the Japanese Utility Model Laid Open Publication No. Hei. 5-47757) as to have a constitution illustrated in FIG. 4 as a small pulse tube refrigerator which is capable of cooling without vibrations. This previously proposed refrigerator has a compressor section (C) comprising a compressor (70), a cooler (71), an oil separator (72) and an oil adsorber (73) arranged in tandem, which is separated from a cold generating section (R), the supply and discharge of the refrigerant gas to and from the cold accumulator (74) constituting the cold generating section (R) being performed by the switching of a rotary valve (75) arranged between the compressor section (C) and the cold generating section (R), a gas reservoir (buffer tank) (78) made of a flexible tube being connected to the high-temperature end portion of the pulse tube (76) through a first orifice (77), and a sub gas passage (80) branched slantly from a main gas passage (79) for communicating the high-temperature end portion of the pulse tube (76) with the gas reservoir (78) being connected through a second orifice (82) to a refrigerant gas passage (81) for communicating the rotary valve (75) with the cold accumulator (74).